Something started happening yesterday in Republican circles in Washington that many people had hoped they'd never have to deal with. Powerful conservatives started calling one another in the wake of John McCain's victory in Tuesday's Florida primary and reconciling themselves to the likelihood that this man they detest is going to be someone they'll have to find a way to support in November.

These conservative operatives and lobbyists and power-brokers, whose animosity toward McCain is well established (and luminously mutual), have held a tremendous amount of sway in the Republican party for 30 years.

Whichever of the three main factions of conservatism they represented, religious, economic or foreign-policy, they have since Reagan's time had the power to sign off on the GOP nominee. In the seven presidential elections since 1980, these power-brokers have been less than enthusiastic twice - in 1992 and 1996, the two times the Republican lost.

McCain still has a long way to go to secure the nomination, and Hillary Clinton's eleventh-hour New Hampshire comeback should warn us off hasty predictions. But the fact that powerful conservatives now have to think really seriously about him as the Republican nominee sets up a fascinating showdown: it's McCain v the party machine.

The key question is: will the machine change him, or will he change it?

The candidate should have the greater leverage here. He's the guy who got the votes. And the voters have repeatedly ignored the power-brokers. Rush Limbaugh, the unchecked id of the right who lives in Florida, spent days fulminating against McCain on his radio show, warning Floridians of the pestilential consequences for the GOP and the country should they elevate the senator from Mordor. Florida Republicans resolutely didn't listen. So McCain ought to be able to take his votes and his delegates into any smoke-filled room of conservative honchos and say: "I got the votes, I call the shots."

But I don't think it's quite that simple. The power-brokers also have a considerable chunk of voters behind them - McCain hasn't won 50% of the vote anywhere, so many more Republicans have voted against him than for him. And they have a lot of party activists behind them - the state committee members, the platform committee members, the people who make the machinery work.

So my guess is if McCain secures the nomination, he will have to make some concessions. He'll need to say he won't pursue immigration reform or campaign-finance legislation. He'll need to pledge new fealty to George Bush's tax cuts, which he voted against. He told The Wall Street Journal editorial board not long ago that he now supported making those tax cuts permanent, but no one on the right seemed to believe him. He'll need to make them believe.

In sum, in the battle of McCain v machine, I think the GOP machine will get the better of him. And that could make the independent and moderate voters who admire him think twice.

What the Democrats do will make a difference here. If they nominate Clinton, she will probably be all the motivation conservatives need. But Barack Obama is a less unifying enemy.

A Clinton nomination, therefore, strengthens McCain's hand, because he can then remind everyone in his party who hates him that they hate her more.

Clinton or no Clinton, McCain will have to do some scraping and bowing. If he can do it with dignity - or better still, in private - so much the better. But it's hard to see how he backs off on some long-held positions, especially on immigration, without looking weak to the independents who admire his strength.